Phytotoxicity of pheromonal chemicals to fruit tree foliage: chemical and physiological characterization.

Some recent high-load, low-density pheromone-release devices emit an ethanolic blend of pheromone directly onto crop foliage to control insect pests by mating disruption. This study characterized the phytotoxicity associated with deposition of some pheromonal compounds in concentrated drops on the foliage of trees bearing aerosol release devices. The relative toxicity of straight-chained alkanes, alcohols, aldehydes, and acetates with chain lengths varying from C-2 to approximately C-20 was quantified in the laboratory by the severity of necrotic lesions. The order of severity for phytotoxicity caused by pheromonal compounds was alkanes < acetates = aldehydes < or = alcohols. Within compound classes tested, pheromones with chain lengths of 6-13 carbons were the most phytotoxic. Phytotoxicity was not detectable at dosages <1 mg administered in 10 microl of ethanol. Phytotoxicity of pheromones was highly correlated with presence of both a hydrophilic and lipophilic molecular domain. We postulate nonspecific membrane disruption as a likely mode of action for pheromonal phytotoxicity. Limited attempts to remediate this effect by changing carrier solvents or adding surfactants, spreaders, or nonvolatile diluents were not successful. Because the toxic action of pheromones upon plant tissues appears relatively benign, and growers have not been adverse to localized phytotoxicity to foliage and fruits on two trees per 0.4 ha, we propose that limited phytotoxicity associated with first-generation aerosol dispenser technology can be viewed as non-threatening.     

Potential for transduction of plasmids in a natural freshwater environment: effect of plasmid donor concentration and a natural microbial community on transduction in Pseudomonas aeruginosa

Transduction of Pseudomonas aeruginosa plasmid Rms149 by the generalized transducing bacteriophage phi DS1 was shown to occur during a 9-day incubation of environmental test chambers in a freshwater reservoir. Plasmid DNA was transferred from a nonlysogenic plasmid donor to a phi DS1 lysogen of P. aeruginosa that served both as the source of the transducing phage and as the recipient of the plasmid DNA. When the concentration of donors introduced into the chambers was varied while the recipient concentration in each chamber was at a level equivalent to natural concentrations of P. aeruginosa, the concentration of plasmid-containing donor cells introduced was shown to affect the frequency of transduction significantly. Transduction was observed both in the absence and in the presence of the natural microbial community. The presence of the natural community resulted in a rapid decrease in the numbers of the introduced donors and recipients and a decrease in the number of transductants recovered. These results demonstrate the potential for naturally occurring transduction in aquatic environments and indicate that donor load may be an important parameter in assessing this potential.     

Chrysonila sitophila (TFB-27441): A hyperlignolytic strain

Summary C. sitophila strain TFB-27441 showed 2–3 times higher lignolytic activity thanPhanerochaete chrysosporium (BKM-F-1767 strain). Lignin had a marked effect on the ligninase activity indicating that some induction or activation mechanism is involved in lignin degradation byC. sitophila.     

Synthesis of a "free" form of hyaluronic acid by articular chondrocytes in monolayer culture

Primary and first passage rabbit chondrocyte cultures synthesized a "free" form of hyaluronic acid (HA-f) previously characterized in rabbit cartilage. HA-f was isolated from the [3H] glcN/35SO4-labelled cell-associated-fraction (CAF) and from the culture medium by successive equilibrium centrifugations in Cs2SO4/CsCl/Cs2SO4 under low salt conditions. The culture medium HA-f appeared in the void volume of Sepharose CL-2B eluted with low salt, (0.5M sodium acetate), and was susceptible to digestion with Streptomyces hyaluronidase. HA-f aggregated purified rabbit cartilage proteoglycan monomer. These results indicated that HA-f probably subserves hyaluronic acid already complexed with proteoglycan monomer. Newly synthesized HA-f may be required for the continual formation of proteoglycan aggregates.     

Localization of vanadium-containing particles in the lungs of uranium/vanadium miners

Several geological formations of the Utah-Colorado mining region mined for uranium ore during and after World War II had been mined earlier for vanadium. Therefore, most miners and millers from that region were exposed to those metals’ ores or tailings at one time or another. Preliminary investigation to determine uranium and vanadium retained in the lungs of a former uranium miner and miller from this region, who died of lung cancer (mesothelioma), showed a high nonuniform distribution of vanadium. This observation led to the hypothesis that the vanadium content in the lungs could be associated with inhaled particles. Further examination of spectra of characteristic X-rays obtained by scanning particle-induced X-ray emission (microPIXE) of an autopsy sample of this lung indicated that vanadium was indeed present in localized sites within the 20-μm spatial resolution of the proton beam. This work points out that the microPIXE-RBS (Rutherford backscattering) test for vanadium can be used for site localization of inhaled particles retained in the lungs. Further studies are in progress to: (i) locate uranium-bearing particles in lung tissues of former uranium miners and millers; and (ii) evaluate the local doses of alpha radiation received from these particles.     

Seasonal changes in density and tissue distribution of Onchocerca cervicalis microfilariae in ponies and related changes in Culicoides variipennis populations in Louisiana

Seasonal changes in density and spatial distribution of Onchocerca cervicalis microfilariae were studied in ventral-midline skin of 15 infected pony mares in southern Louisiana. Triple running mean analysis of data over a 13-mo period indicated that a distinct pattern exists in total microfilariae population density and in microfilariae occurrence in different levels of the dermis. Microfilariae density reaches peak levels in the spring followed by a 58% decrease in the summer, a 19% increase in the fall, and a decrease to the lowest numbers in the winter. Microfilariae were found in all levels of the skin during the spring, summer, and fall but were not found in the superficial layers of the dermis during the winter months. The population density of Culicoides variipennis, a demonstrated vector of O. cervicalis, appeared to have seasonal fluctuations similar to the changes in microfilarial density. Harmonic wave analysis of microfilariae density data in individual ponies showed that all individuals did not follow the population trend.     

Differences among human immunodeficiency virus strains in their capacities to induce cytolysis or persistent infection of a lymphoblastoid cell line immortalized by Epstein-Barr virus.

Four strains of human immunodeficiency virus (HIV) manifest consistent differences in biologic behavior after infection of the X50-7 line of human umbilical cord lymphocytes immortalized by Epstein-Barr virus (EBV). Some dilutions of the first strain examined, human T-cell lymphotropic virus type III B, which is derived from a pool of patient isolates propagated in H9 cells, caused transient cytopathic effects (CPE) followed by recovery of a subpopulation of X50-7 cells which became virus carrier cultures. Other dilutions of the same virus stock completely lysed X50-7 cells. Two other strains, RF2 and YW, both from individual patients with acquired immune deficiency syndrome, always induced complete cytolysis of X50-7 cells at all dilutions which infected the cells. However, RF2 did establish persistent infection of H9 cells. A fourth strain, PH1-MN, from a child with acquired immune deficiency syndrome-related complex, induced only transient CPE in X50-7 and H9 cells, which thereafter always recovered to form carrier cultures. For all four strains, the dilutions of HIV stocks which caused CPE corresponded to dilutions which resulted in the detection of HIV polypeptides by immunoblot. Cytolysis in HIV-infected X50-7 cells was accompanied by a decrease in the amount of EBV nuclear antigen; however, HIV infection did not induce EBV replication. Thus CPE in X50-7 cells is due to replication of HIV per se and not to activation of EBV. The observations indicate that there are differences in the cytolytic properties of HIVs and that these differences are influenced by the target cell.     

An evaluation of the recycling in measurements of photorespiration

All measurements of photorespiration and gross photosynthesis in leaves, whether using isotopes or not, are underestimated because of the recycling of O₂ or CO₂. On the basis of a simple diffusion model, we propose a method for the calculation of the recycling and the corresponding underestimation of the measurements. This procedure can be applied when the stomatal resistance is known, and allows for a correction of certain results in the literature. It is found that measurements of the photorespiratory CO₂ release are usually underestimated by 20 to 100%, which sets the estimated rate of CO₂ photorespired at 30 to 50% of the net photosynthesis in C3 plants under normal conditions. In water stress studies, the correction of the photorespiration is still more important (1.5-3.3) because the stomata are closed more. Analysis of the diffusion of O₂ shows that its recycling is low and that the underestimation of photorespiration with ¹⁸O₂ is negligible.