Structure-activity relationships of DDT-type analogs based on in vivo toxicity to the sensory nerves of the cockroach, Periplaneta americana L

Forty-three DDT-type compounds were applied in saline suspension to the crural nerve of Periplaneta americana L. and the threshold concentration (ED₅₀) to produce trains of impulses was determined together with the frequency of appearance of repetitive afterdischarge. These quantitative neurological measures were evaluated in multiple regression analyses of structural parameters including van der Waal's volume, the F and R components of Hammet's σ, and the hydrophobic constant Π. This structure-activity analysis provides an accurate estimation of the intrinsic toxicity of the DDT analogs. The results affirm previous working theories that the bulk of the functional groups within the DDT framework is the primary factor relating to activity. However, conformation is also an important parameter.     

Insecticidal activity of N-arylalkylbenzhydrolpiperidines

Benzhydrolpiperidine (BZP) insecticides represent a novel class of chemistry. Their specificity and efficacy as well as their low mammalian toxicity give them excellent potential for commercialization. Several N-arylalkylbenzhydrolpiperidines were tested for activity against a variety of insects in the laboratory and greenhouse. These tests were used to select compounds for field trials and determine rates of application for field tests. The BZP compounds have good activity against Lepidoptera, with modest Coleoptera activity. They are toxic by oral administration and have about 100-fold lower activity by topical exposure. A methyl carbamate BZP, F4265, was the most active compound, with LC50 values of 6 mg litre(-1) or less for most Lepidopteran species tested. F4265 was active in a variety of field trials at 112-224gAI ha(-1). Whole-plant testing methods conducted in the greenhouse were effective in determining field test rates.     

Period of susceptibility of almonds to aflatoxin contamination during development in the orchard

Almonds can be contaminated with aflatoxins, produced mainly by Aspergillus flavus and A. parasiticus. Infection can be facilitated by insect injuries during hull split, which begins four to six weeks before harvest. Within this period, it is unknown which kernel stages are most susceptible to aflatoxin contamination. Developing almonds of the Nonpareil cultivar were inoculated weekly with a spore suspension of A. flavus or A. parasiticus for five weeks after hull split in 2013. The almonds were infested with eggs of the lepidopteron navel orangeworm (NOW) (Amyelois transitella) before each spore inoculation. Aflatoxin levels were quantified at harvest using HPLC. Aflatoxin contamination was consistently higher in NOW-damaged kernels, although aflatoxins were also detected in undamaged kernels at each inoculation date. Insect injury is not required for kernel infection but it is a key risk factor for high aflatoxin contamination. Laboratory inoculations were also performed on Nonpareil almond kernels collected during the summers of 2013 and 2015. Aflatoxin levels were significantly lower on dried almonds but the ability to produce aflatoxins was restored when almonds were incubated with high humidity or when the Aspergillus species were inoculated on almond meal agar amended with ground kernels. Therefore, aflatoxins can accumulate in kernels with low a_w, should sufficient moisture favors aflatoxin production. In our field experiment, the orchard micro-climate had sufficient humidity to enable aflatoxin production in both damaged and undamaged dried kernels.     

Planning for success: Identifying effective and efficient survey designs for monitoring

Selecting a survey design to detect change through time in an ecological resource requires balancing the speed with which a given level of change can be detected against the cost of monitoring. Planning studies allow one to assess these tradeoffs and identify the optimal design choices for a specific scenario of change. However, such studies seldom are conducted. Even worse, they seem least likely to be undertaken when they offer the most insight – when survey methods and monitoring designs are complex and not well captured by simple statistical models. This may be due to limited technical capacity within management agencies. Without such planning, managers risk a potentially severe waste of monitoring resources on ineffective and inefficient monitoring, and institutions will remain ignorant of the true costs of information and the potential efficiency gains afforded by a moderate increase in technical capacity. We discuss the importance of planning studies, outline their main components, and illustrate the process through an investigation of competing designs for monitoring for declining brown bear (Ursus arctos) densities in southwestern Alaska. The results provide guidance on how long monitoring must be sustained before any change is likely to be detected (under a scenario of rather strong true decline), the optimal designs for detecting a change, and a tradeoff where accepting a delay of 2 years in detecting the change could reduce the monitoring cost by almost 50%. This report emphasizes the importance of planning studies for guiding monitoring decisions.     

Degradation of an Atrazine and Metolachlor Herbicide Mixture in Pesticide-Contaminated Soils from Two Agrochemical Dealerships in Iowa

The fate of atrazine and metolachlor,applied as a mixture, in soil taken from twopesticide-contaminated sites in Iowa (denoted as Alphaor Bravo) were determined in laboratory studies. Atrazine and metolachlor degradation, as well asatrazine mineralization, were greater in soilcollected from Kochia scoparia L. (Schrader)rhizosphere than in soils from unvegetated areas. Theradiolabeled ¹⁴C-carbinol and¹⁴C-morpholinone metabolites were identified in¹⁴C-metolachlor-applied soil 60 d aftertreatment. The half-life for atrazine in Alpha soilwas significantly less in the rhizosphere soil (50 d)than in unvegetated soil (193 d). Quantities ofspecific atrazine degraders were one to two orders ofmagnitude greater in Bravo soils than in Alpha soils. In an experiment with plants present, significantlymore ¹⁴C-atrazine was taken up by K.scoparia (9.9% of the applied ¹⁴C) than by Brassica napus L. Significantly less atrazine wasextractable from soils vegetated with K.scoparia than from soils vegetated with B.napus or unvegetated soils.     

Natural compounds derived from foods modulate nitric oxide production and oxidative status in epithelial lung cells

The effects of natural antioxidants on nitric oxide (NO) modulation and oxidative status were determined in rat epithelial lung cells (L-2). Cells were stimulated with cytokines and treated with one of the following: resveratrol, soybean saponin group B (SSB), quercetin, genistein, olive leaf polyphenol concentrate (OLPC), or N-acetyl-L-cystein (NAC). NAC had no effect on NO levels, whereas resveratrol and OLPC were found to be effective in reducing nitrite levels, modifying iNOS mRNA, and decreasing free radical production. OLPC affected the levels of MnSOD while resveratrol did not, indicating that they act via different pathways. Quercetin and genistein reduced nitrite levels without affecting iNOS levels, presumably by scavenging NO. SSB did not affect nitrite levels, but exposure did reduce iNOS mRNA expression and protein levels, possibly due to antioxidant activity. Naturally occurring antioxidants, in particular resveratrol and OLPC, may have therapeutic potential in the treatment of inflammatory diseases.