Influence of aerial dispersal on persistence and spread of pesticide-resistant Metaseiulus occidentalis in California almond orchards

Aerial dispersal of the phytoseiid Metaseiulus occidentalis (Nesbitt) was evaluated as a component in managing pesticide-resistant populations established in California almond orchards. Peak dispersal occurred in late July and early August during 1982 and 1983. Most predators (and spider mites) left the orchards on the prevailing winds from the northwest. Within the orchard, the prevailing winds had less influence, and dispersal was usually random. Both spider mites and predators dispersed randomly with regard to height from the almond trees, but data obtained during one 24-h interval suggest they do not disperse randomly throughout the day. Most aerial movements occurred between 16–22 h when relative humidity and wind speeds increased and temperatures decreased. Spider mites and predators were trapped on panels located 200 m from the orchard. A survey of carbaryl resistance levels in M. occidentalis collected from almond orchards surrounding the release sites indicates that carbaryl-resistant M. occidentalis dispersed at least 800 m between 1981–83. However, growers wishing to use the resistant strains should release them in their orchards as natural dispersal appears to be too slow. Migration of native M. occidentalis into the release sites appeared to be sufficiently rare that dilution of carbaryl-resistant populations was minimal during a 2–4 year period.

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Résumé La dispersion aérienne du phytoseïdae, M. occidentalis (Nesbitt), a été estimée comme élément de la lutte contre les populations résistantes aux insecticides établies dans les vergers de Californie. La dispersion maximale s'est produite fin juillet et début a oût en 1982 et 1983. La plupart des prédateurs (et des acariens) quittent les vergers avec les vents dominants du nordouest. Dans le verger, les vents dominants sont moins importants et la dispersion est généralement au hasard. Tant les acariens que les prédateurs se dispersaient au hasard par rapport à la taille des amandiers, mais les relevés sur 24 heures laissent supposer qu'il n'y a pas une distribution aléatoire pendant la journée. La plupart des mouvements aériens se produisirent entre 16 et 22 heures quand HR et vitesse du vent augmentaient et température diminuait. Les acariens et prédateurs ont été piégés sur des panneaux à 200 m du verger.

     

Germination-initiated spores of Bacillus brevis Nagano retain their resistance properties.

Initiated spores and vegetative cells of the gramicidin S-producing Bacillus brevis Nagano were compared with respect to their resistance to various forms of stress (osmotic shock-starvation, exposure to ethanol, sonic oscillation, and heat). The resistance of initiated spores to all of these stress situations was considerably greater than that of vegetative cells and approached that of dormant spores. The period during which the initiated spores remained resistant to heat was extended by addition of gramicidin S. The antibiotic may therefore be of survival value to the species in nature by slowing down the development of initiated spores in the outgrowth phase of germination, thereby extending the period during which the cells are resistant to environmental stress.     

Proteoglycans from bovine nasal and articular cartilages. Fractionation of the link proteins by wheat germ agglutinin affinity chromatography

Two forms of link protein, 46 and 51 kDa, are present in proteoglycan aggregates from both bovine nasal and bovine articular cartilages. Studies reported here show that the link proteins bind to concanavalin A, Lens culinaris agglutinin, Ricinus communis agglutinin, soybean agglutinin, and wheat germ agglutinin lectins. When the link proteins are eluted from these lectins with appropriate competing sugars, the 46- and the 51-kDa link proteins elute together and no separation is achieved. However, when the link proteins bound to wheat germ agglutinin are eluted with a 0 to 4 M guanidine hydrochloride linear gradient, a good separation of the 46- and 51-kDa link proteins is achieved. Wheat germ agglutinin affinity chromatography has been used on a preparative scale to isolate the 51-kDa link protein from mature bovine articular cartilage to homogeneity, in amounts sufficient to examine its effect on proteoglycan aggregate size and stability in sedimentation velocity studies. Proteoglycan aggregates were reassembled from proteoglycan monomers and hyaluronate in the absence of link protein, in the presence of both 46- and 51-kDa link proteins, and in the presence of the individual 51-kDa link protein. The sizes of the aggregates were compared in terms of sedimentation coefficients (s(0)20). The stability of the aggregates was compared in terms of the per cent aggregate present at pH 7 and 5. At pH 7, the sedimentation coefficients (s(0)20) of link-free aggregates, aggregates formed with both link proteins, and aggregates formed with 51-kDa link protein were 72, 93, and 112 S, respectively. Thus, the 51-kDa link protein has a pronounced effect on aggregate size. The link-free aggregate was grossly unstable, and only 36% aggregate was present at pH 5. The aggregate formed with both link proteins was effectively stabilized against dissociation and 79% aggregate was present at pH 5. The aggregate formed with 51-kDa link protein was not effectively stabilized against dissociation, and only 60% aggregate was present at pH 5. Thus, despite its pronounced effect on aggregate size, the 51-kDa link protein does not effectively stabilize the proteoglycan aggregate against dissociation. These results suggest that the 51-kDa link protein may selectively increase aggregate size, while the 46-kDa link protein may be required to effectively stabilize the proteoglycan aggregate against dissociation.     

Allosteric Modulation of Flunitrazepam Binding to Rat Brain Benzodiazepine Receptors by Methyl β-Carboline-3-Carboxylate

The inhibition of flunitrazepam (FNP) binding to rat brain benzodiazepine (BZ) receptors by methyl beta-carboline-3-carboxylate (MCC) was studied. Biphasic dissociation was observed for [3H]FNP and [3H]MCC in cerebral cortex, cerebellum, and hippocampus, although the dissociation of [3H]MCC was much faster. The dissociation rate of [3H]FNP was increased by MCC in the cerebellum, but was not altered in cerebral cortex or hippocampus. [3H]FNP binding stimulated by gamma-aminobutyric acid was enhanced in the presence of MCC in all three regions examined. These results indicate that MCC exerts these effects by interacting with allosteric sites that are different from the FNP recognition sites on the BZ receptors.     

Autocides produced by Myxococcus xanthus.

Ethanol extracts of Myxococcus xanthus contained several substances, referred to as autocides, which were bactericidal to the producing strain but showed no activity against other bacteria. The autocides were produced by growing cells and remained largely cell bound throughout the growth cycle; ca. 5% of the autocidal activity was found in the supernatant fluid at the time cell lysis began. The autocides were separated by sequential-column and thin-layer chromatography into five active fractions (AM I through AM V). Each of the fractions was at least 20 times more active against M. xanthus than against the other gram-negative or gram-positive bacteria tested. AM I, AM IV, and AM V were inactive against yeasts, whereas a mixture of fractions AM II and AM III was active against Rhodotorula sp. At low concentrations, AM I reversibly inhibited the growth of M. xanthus; at higher concentrations of AM I, the cells lysed within 1 h. The lowest concentration of AM IV that showed any activity caused rapid cell death and lysis. The mode of action of the major autocide, AM V, was different from that of AM I and AM IV. During the initial 2 h of treatment, the viable count of M. xanthus cells remained constant; during the next few hours killing occurred without lysis; within 24 h lysis was complete. The autocidal activity of each of the fractions was expressed when the cells were suspended in buffer, as well as in growth medium. The possible role of autocides in developmental lysis of M. xanthus is discussed.     

Transfer of Rhizobium meliloti pSym genes into Agrobacterium tumefaciens: host-specific nodulation by atypical infection

The pSym megaplasmid of Rhizobium meliloti 2011 mobilized by plasmid RP4, or plasmid pGMI42, an RP4-prime derivative which carries a 290-kilobase pSym fragment including nitrogenase and nod genes, was introduced into Agrobacterium tumefaciens. The resulting transconjugants induced root deformations specifically on the homologous hosts Medicago sativa and Melilotus alba and not on the heterologous hosts Trifolium pratense and Trifolium repens. The root deformations were shown to be genuine nodules by physiological and cytological studies. Thus, host specificity nodulation genes are located on the pSym megaplasmid. Host nodulation specificity did not seem to require recognition at the root hair level since no infection threads could be detected in the root hairs. Cytological observations indicated that bacteria penetrated only the superficial layers of the host root tissue by an atypical infection process. The submeristematic zone and the central tissue of the nodules were bacteria free. Thus, nodule organogenesis was probably triggered from a distance by the bacteria. Agrobacterium transconjugants carrying pSym induced the formation of more numerous and larger nodules than those carrying the RP4-prime plasmid pGMI42, suggesting that some genes influencing nodule organogenesis are located in a pSym region(s) outside that which has been cloned into pGMI42.     

Rapid turnover of mannitol-1-phosphate in Escherichia coli.

The phosphate moiety of D-mannitol-1-phosphate in Escherichia coli is subject to rapid turnover and is in close equilibrium with Pi and the phosphorus of fructose-1,6-bisphosphate. These three compounds account for the bulk of 32P label found in cells after several minutes of uptake of 32Pi and mannitol-1-phosphate represents some 30% of this label. Mannitol-1-phosphate occurs in E. coli grown on a variety of carbon sources, in the absence of D-mannitol, and is synthesized de novo even in mutants lacking mannitol-1-phosphate dehydrogenase. The mannitol moiety of mannitol-1-phosphate was not affected during the total chase of the P moiety, which exchanged with a half-life of about 30 s. These findings suggest that the rapid equilibration of the phosphorus is a function of an enzyme, possibly a component of the phosphotransferase system, capable of forming a complex that allows the exchange of the phosphate without the equilibration of the mannitol moiety with free mannitol.     

Role of actin binding protein phosphorylation in platelet cytoskeleton assembly

Actin binding protein from human blood platelets is shown to exist in the resting platelet as a phosphorylated protein and contains two residues of phosphate per 260,000 kd. Removal of one-half of these residues with E. coli alkaline phosphatase results in the loss of its ability to crosslink F-actin into a low speed sedimentable complex (its cytoskeleton) and to bind to an F-actin affinity column. Thus, phosphorylation-dephosphorylation of ABP may be an important regulatory mechanism by which the platelet regulates its shape via its cytoskeletal structure.