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981.
Zhu KY Wilde GE Higgins RA Sloderbeck PE Buschman LL Shufran RA Whitworth RJ Starkey SR He F 《Journal of economic entomology》2001,94(4):929-934
Susceptibility of adult populations of the western corn rootworm, Diabrotica virgifera virgifera LeConte, to carbaryl was determined by a survey in 1996 before the implementation of an areawide management program near Scandia in north central Kansas. Subsequently, the susceptibility of western corn rootworm adults to carbaryl has been monitored throughout the program from 1997 to 2000 in both control and managed areas. In 1996, adults were highly susceptible to carbaryl with a mean LC50 value of 0.64 microg/vial. This value was comparable to those for adults collected from other regions within Kansas. However, adult susceptibility to carbaryl decreased rapidly within the managed area, where the cucurbitacin- carbaryl-based bait SLAM has been used as the primary tool to control adults in this project since 1997. In 1999, adults collected from the managed area were 9- and 20-fold less susceptible to carbaryl at the LC50 and LC90 levels, respectively, than those evaluated in 1996. In contrast, adults collected from the control area were only 2- and 3-fold less susceptible to carbaryl at the LC50 and LC90 levels, respectively, than adults evaluated in 1996. Although field adult populations of western corn rootworm were relatively low in 2000, evaluations showed trends similar to those in 1999 regarding their carbaryl susceptibility in the managed and control areas. These results provide evidence that western corn rootworm has been evolving carbaryl resistance rapidly in response to the use of SLAM in areawide-managed cornfields near Scandia. 相似文献
982.
BACKGROUND: To investigate the effect of body temperature and moisture on body fat (%fat), volume and density by air-displacement plethysmography (BOD POD). METHODS: %fat, body volume and density by the BOD POD before (BOD PODBH) and immediately following hydrostatic weighing (BOD PODFH) were performed in 32 healthy females (age (yr) 33 +/- 11, weight (kg) 64 +/- 14, height (cm) 167 +/- 7). Body temperature and moisture were measured prior to BOD PODBH and prior to BOD PODFH with body moisture defined as the difference in body weight (kg) between the BOD PODBH and BOD PODFH measurements. RESULTS: BOD PODFH %fat (27.1%) and body volume (61.5 L) were significantly lower (P = 0.001) and body density (1.0379 g/cm3) significantly higher (P = 0.001) than BOD PODBH %fat (28.9%), body volume (61.7 L), and body density (1.0341 g/cm3). A significant increase in body temperature (~0.6 degrees C; P = 0.001) and body moisture (0.08 kg; P = 0.01) were observed between BOD PODBH and BOD PODFH. Body surface area was positively associated with the difference in %fat independent of changes in body temperature and moisture, r = 0.30, P < 0.05. CONCLUSION: These data demonstrate for the first time that increases in body heat and moisture result in an underestimation of body fat when using the BOD POD, however, the precise mechanism remains unidentified. 相似文献
983.
Comparative analysis of proteinase activities of Bacillus thuringiensis-resistant and -susceptible Ostrinia nubilalis (Lepidoptera: Crambidae) 总被引:1,自引:0,他引:1
Li H Oppert B Higgins RA Huang F Zhu KY Buschman LL 《Insect biochemistry and molecular biology》2004,34(8):753-762
Proteinase activities were compared in soluble and membrane fractions of guts obtained from larvae of Bacillus thuringiensis-resistant and -susceptible Ostrinia nubilalis. Overall, serine proteinases from soluble fractions of the susceptible strain were more active than those of the resistant strain. The soluble trypsin-like proteinase activity of the resistant strain was approximately half that of the susceptible strain. The number and relative molecular masses of soluble and membrane serine proteinases were different. However, there were no significant differences in the activities of serine proteinases and aminopeptidases extracted from midgut membranes of the two strains. Cry1Ab protoxin hydrolysis by soluble proteinase extracts of the resistant strain was reduced approximately 20-30% relative to that of the susceptible strain. Reduced protoxin processing due to decreased activities of Bt protoxin activation proteinases may be associated with resistance to Bt toxin in this resistant strain of O. nubilalis. 相似文献
984.
Repacking of the transmembrane domains of P-glycoprotein during the transport ATPase cycle 总被引:15,自引:0,他引:15
Rosenberg MF Velarde G Ford RC Martin C Berridge G Kerr ID Callaghan R Schmidlin A Wooding C Linton KJ Higgins CF 《The EMBO journal》2001,20(20):5615-5625
P-glycoprotein (P-gp) is an ABC (ATP-binding cassette) transporter, which hydrolyses ATP and extrudes cytotoxic drugs from mammalian cells. P-gp consists of two transmembrane domains (TMDs) that span the membrane multiple times, and two cytoplasmic nucleotide-binding domains (NBDs). We have determined projection structures of P-gp trapped at different steps of the transport cycle and correlated these structures with function. In the absence of nucleotide, an approximately 10 A resolution structure was determined by electron cryo-microscopy of two-dimensional crystals. The TMDs form a chamber within the membrane that appears to be open to the extracellular milieu, and may also be accessible from the lipid phase at the interfaces between the two TMDs. Nucleotide binding causes a repacking of the TMDs and reduction in drug binding affinity. Thus, ATP binding, not hydrolysis, drives the major conformational change associated with solute translocation. A third distinct conformation of the protein was observed in the post-hydrolytic transition state prior to release of ADP/P(i). Biochemical data suggest that these rearrangements may involve rotation of transmembrane alpha-helices. A mechanism for transport is suggested. 相似文献
985.
Three-dimensional domain swapping in the folded and molten-globule states of cystatins, an amyloid-forming structural superfamily 总被引:1,自引:0,他引:1 下载免费PDF全文
Staniforth RA Giannini S Higgins LD Conroy MJ Hounslow AM Jerala R Craven CJ Waltho JP 《The EMBO journal》2001,20(17):4774-4781
Cystatins, an amyloid-forming structural superfamily, form highly stable, domain-swapped dimers at physiological protein concentrations. In chicken cystatin, the active monomer is a kinetic trap en route to dimerization, and any changes in solution conditions or mutations that destabilize the folded state shorten the lifetime of the monomeric form. In such circumstances, amyloidogenesis will start from conditions where a domain-swapped dimer is the most prevalent species. Domain swapping occurs by a rearrangement of loop I, generating the new intermonomer interface between strands 2 and 3. The transition state for dimerization has a high level of hydrophobic group exposure, indicating that gross conformational perturbation is required for domain swapping to occur. Dimerization also occurs when chicken cystatin is in its reduced, molten-globule state, implying that the organization of secondary structure in this state mirrors that in the folded state and that domain swapping is not limited to the folded states of proteins. Although the interface between cystatin-fold units is poorly defined for cystatin A, the dimers are the appropriate size to account for the electron-dense regions in amyloid protofilaments. 相似文献
986.
987.
988.
Alice Rothnie Daniel Theron Loredana Soceneantu Catherine Martin Mounir Traikia Georgina Berridge Christopher F. Higgins Philippe F. Devaux Richard Callaghan 《European biophysics journal : EBJ》2001,30(6):430-442
In tumour cell lines that display multidrug resistance, expression of P-glycoprotein (P-gp) alters many aspects of biomembrane organization in addition to its well-characterized drug transport activity. We have developed a reconstitution system to directly investigate the effect of purified P-gp on the biophysical properties of lipid bilayers. Using a mixed detergent system it was possible to efficiently reconstitute P-gp at lipid:protein ratios as low as 2.5 (w/w) by removal of detergent using adsorption to SM-2 BioBeads. P-gp was able to alter many biophysical parameters associated with lipid organization within bilayers. For example, the changes in overall fluidity and excimer formation by lipid analogues indicate modified packing organization of bilayer constituents. Surprisingly, given its role in conferring drug resistance, P-gp insertion into bilayers also caused significantly increased permeability to aqueous compounds, also reflecting a modified phospholipid environment. Translocation of various phospholipid species between leaflets of the bilayer was increased in the presence of P-gp; however, the effect was not dependent on ATP hydrolysis by the protein. Physiological concentrations of cholesterol modified P-gp function and the degree to which it perturbed bilayer organization. The basal ATPase activity of P-gp was increased in a dose-dependent fashion by the incorporation of cholesterol in PC:PE liposomes. In addition, the degree to which the modulator verapamil was able to stimulate this basal ATPase activity was reduced by the presence of cholesterol in proteoliposomes. However, the potency of verapamil was unaltered, suggesting a specific effect, not simply caused by lower drug penetration into the cholesterol containing bilayers. In summary, P-gp is able to cause perturbation in the organization of bilayer constituents. Cholesterol imparted "stability" to this perturbation of bilayer organization by P-gp and moreover this led to altered protein function. 相似文献
989.
Concordance of murine quantitative trait loci for salt-induced hypertension with rat and human loci 总被引:27,自引:0,他引:27
Sugiyama F Churchill GA Higgins DC Johns C Makaritsis KP Gavras H Paigen B 《Genomics》2001,71(1):70-77
To investigate the genetic control of salt-induced hypertension, we performed a quantitative trait locus analysis on male mice from a reciprocal backcross between the salt-sensitive C57BL/6J and the normotensive A/J inbred mouse strains after they were provided with water containing 1% salt for 2 weeks. Genome-wide scans performed on these mice and analyzed with a combination of conventional marker-based regressions and a novel simultaneous search for pairs revealed six significant quantitative trait loci associated with salt-induced blood pressure, two of which were interacting loci. These six loci, named Bpq1-6 for blood pressure quantitative trait loci, mapped to D1Mit334, D1Mit14, D4Mit164, D5Mit31, D6Mit15, and D15Mit13. Furthermore, five of these six loci were concordant with hypertension loci in rats, and four were concordant with hypertension loci in humans, suggesting that quantitative trait loci mapping in model organisms can be used to guide the search for human blood pressure genes. 相似文献
990.