Interaction between the black yeast Aureobasidium pullulans and the gall midge Lasioptera ephedricola in gall formation on the desert shrub Ephedra trifurca

Galls produced by the cecidomynd Lastoptera ephedncola on Ephedia trifurca always have a black ring associated with them while galls produced by the congener L ephedrae never do Black ring material after microscopic examination and culture proved to be Aureobasidium pullulans In addition to lacking black ring material neither L ephedrae galls nor healthy stems consistently yielded Aureobasidium on culture Gall and larva size measurements indicated that continued larval presence is not necessary for gall development, suggesting fungus initiated gall formation However inoculation of healthy stems with Aureobasidium caused lesions hut not galls The mycelium m galls did not appear grazed and neither larvae nor pupae contained Aureobasidium propagules suggesting that larvae do not feed directly on fungi These data also suggest that there is no trans-pupal passage of fungus from larvae or pupae to adults Newly emerged females do not carry fungal propagules suggesting that thcy are not inoculated upon exiting the gall Gall position leaf culture and stem culture data suggest that the fungus is picked up from leaves prior to oviposition     

Ronald Ross and the malaria-mosquito cycle

This essay examines briefly Ronald Ross's research on malaria in India between 1895 and 1899, during which time he elucidated the role of the Anopheles mosquito in the transmission of the disease. During his crucial experimental work in 1898, he used birds, human malaria being relatively uncommon in Calcutta. This article is based largely on the correspondence between Ross and Patrick Manson, which has just been edited.     

Spectroscopic investigations of intermediates in the reaction of cytochrome P450BM3–F87G with surrogate oxygen atom donors

Rapid mixing of substrate-free ferric cytochrome P450_BM3–F87G with m-chloroperoxybenzoic acid (mCPBA) resulted in the sequential formation of two high-valent intermediates. The first was spectrally similar to compound I species reported previously for P450_CAM and CYP 119 using mCPBA as an oxidant, and it featured a low intensity Soret absorption band characterized by shoulder at 370 nm. This is the first direct observation of a P450 compound I intermediate in a type II P450 enzyme. The second intermediate, which was much more stable at pH values below 7.0, was characterized by an intense Soret absorption peak at 406 nm, similar to that seen with P450_CAM [T. Spolitak, J.H. Dawson, D.P. Ballou, J. Biol. Chem. 280 (2005) 20300–20309]. Double mixing experiments in which NADPH was added to the transient 406 nm-absorbing intermediate resulted in rapid regeneration of the resting ferric state, with the flavins of the flavoprotein domain in their reduced state. EPR results were consistent with this stable intermediate species being a cytochrome c peroxidase compound ES-like species containing a protein-based radical, likely localized on a nearby Trp or Tyr residue in the active site. Iodosobenzene, peracetic acid, and sodium m-periodate also generated the intermediate at 406 nm, but not the 370 nm intermediate, indicating a probable kinetic barrier to accumulating compound I in reactions with these oxidants. The P450 ES intermediate has not been previously reported using iodosobenzene or m-periodate as the oxygen donor.     

Banks grass mite (Oligonychus pratensis) abundance on sorghum cultivars with different levels of nitrogen use and metabolism efficiency

Banks grass mite (Oligonychus pratensis (Banks)), abundance was recorded for three years on sorghum (Sorghum bicolor (L.) Moench) cultivars with different levels of nitrogen (N) use and metabolism efficiency. The cultivars included 77CS1, SC630-11E, R6956, and SC325-12. Nitrogen fertilizer was applied to plots containing each cultivar at 0,45, and 180 kg Na ha^–1. Significantly more mites were on plants at 180 kg N ha^–1 than at 0 or 45 kg N ha^–1. The lowest mite densities were recorded on SC325-12, the N-use-inefficient and N-metabolism-efficient cultivar. In July,O. pratensis abundance was statistically equivalent on SC325-12 and on R6956, the other N-metabolism-efficient cultivar. In August, mite densities on R6956 were as high as on 77CS1 and SC630-11E, which are N-metabolism-ineficient cultivars. Mite densities were lower on N-use-inefficient and N-metabolism-efficient sorghum cultivars than on their respective efficiency counterparts. Physiological differences in N-use and metabolism-inefficient cultivars may influence the amount of leaf N plus the amount and form of amino acids and other N-based chemicals in sorghum leaves. These plant chemicals have been shown to influence mite abundance on several hosts, and may have been key to influencing the results of these experiments.     

IL-1beta decreases the elastic modulus of human tenocytes.

Cellular responses to mechanical stimuli are regulated by interactions with the extracellular matrix, which, in turn, are strongly influenced by the degree of cell stiffness (Young's modulus). It was hypothesized that a more elastic cell could better withstand the rigors of remodeling and mechanical loading. It was further hypothesized that interleukin-1beta (IL-1beta) would modulate intracellular cytoskeleton polymerization and regulate cell stiffness. The purpose of this study was to investigate the utility of IL-1beta to alter the Young's modulus of human tenocytes. Young's modulus is the ratio of the stress to the strain, E = stress/strain = (F/A)/(deltaL/L0), where L0 is the equilibrium length, deltaL is the length change under the applied stress, F is the force applied, and A is the area over which the force is applied. Human tenocytes were incubated with 100 pM recombinant human IL-1beta for 5 days. The Young's modulus was reduced by 27-63%. Actin filaments were disrupted in >75% of IL-1beta-treated cells, resulting in a stellate shape. In contrast, immunostaining of alpha-tubulin showed increased intensity in IL-1beta-treated tenocytes. Human tenocytes in IL-1beta-treated bioartificial tendons were more tolerant to mechanical loading than were untreated counterparts. These results indicate that IL-1beta reduced the Young's modulus of human tenocytes by disrupting the cytoskeleton and/or downregulating the expression of actin and upregulating the expression of tubulins. The reduction in cell modulus may help cells to survive excessive mechanical loading that may occur in damaged or healing tendons.     

Susceptibility of populations of Banks grass mites (Acari: Tetranychidae) suspected of developing bifenthrin resistance from three maize fields

Banks grass mite, Oligonychus pratensis (Banks), from three Texas maize fields were assayed for bifenthrin resistance following poor field control in 1995. Laboratory bioassays showed the field mites to be 3- to 23-fold more tolerant to bifenthrin than the susceptible laboratory culture. Comparison of LC₅₀ values to assays with bifenthrin from 1985 to 1993 indicated no statistically significant changes in mite resistance. However, high LC₉₀ values in 1995 suggest possible resistance development. The percentages of resistant mites from the three fields in 1995 were calculated to be 4.7%, 17.9%, and 30.9%. The Banks grass mite population exhibiting the highest level of tolerance to bifenthrin was further assayed to evaluate tolerance levels to other insecticides alone and in combination with synergists and insecticides. A high level of tolerance existed in the 1995 ‘bifenthrin–selected’ Banks grass mite strain to bifenthrin, dimeothate, and amitraz. The combination of bifenthrin or dimethoate with a synergist indicated changes in the ability of the more resistant 1995 mites to detoxify insecticides. The activity of a dimethoate + bifenthrin mixture and a three way mixture of dimethoate, bifenthrin, and piperonyl butoxide caused 5- and 38-fold increase in toxicity against the more resistant Banks grass mite. This revised version was published online in July 2006 with corrections to the Cover Date.     

Identifying insecticide-resistant greenbugs (Homoptera: Aphididae) with diagnostic assay tests

Laboratory bioassays were used to develop a diagnostic assay test for identifying greenburg, Schizaphis graminum (Rondani), populations that are insecticide-resistant. Petri dish assays with chlorpyrifos showed greenbug mortality should be monitored after 2 h of exposure. One-hour exposure did not kill a high percentage of susceptible greenbugs, and a 3-h exposure killed too many resistant greenbugs. Ethanol and methanol were both good solvents for mixing with chlorpyrifos in the petri dish assay. From the laboratory bioassays, four diagnostic concentrations of chlorpyrifos (3, 10, 30, and 100 ppm) were evaluated in the field by Texas A&M University agricultural research and extension entomologists across the Texas High Plains. Results from the diagnostic assay tests were compared with gel-electrophoresis resistance tests to validate resistance detection. The diagnostic assay tests gave the same greenbug resistance identification as the gel-electrophoresis analysis in 21 of 22 field bioassays in 1994 and 35 of 39 field bioassays in 1995. Diagnostic concentrations of 30 and 100 ppm chlorpyrifos killed > or = 85 and > or = 90%, respectively, of greenbugs identified by gel-electrophoresis as susceptible and < 40% and < 55%, respectively, of resistant greenbugs. The diagnostic assay technique is a quick, reliable, and inexpensive method for detecting insecticide resistance in greenbug populations.