Dispersal Behaviour and Transmission Strategies of the Entomopathogenic Nematodes Heterorhabditis and Steinernema

Entomopathogenic nematodes of the Heterorhabditidae and Steinernematidae appear to be capable of long-distance dispersal and local migration. Their transmission strategies include both highly active seek-and-destroy behaviours and ambusher strategies, and they may be sensitive to sex-related factors in their own populations. Their host-finding abilities are poorly understood, despite the fact that these abilities are fundamental to their success as biocontrol agents in soil. Like the vast numbers of exotic hymenopterans and other natural enemies that have been released for biological control over the past century, they may be used in their ecologically competent wild-type form. On the other hand, because they are applied inundatively, they may be tailored, by breeding or transformation, to their intended purpose and to ecological incompetence, improving both their efficacy and their ecological safety.     

Differential Effects of Pratylenchus neglectus Populations on Single and Interplantings of Alfalfa Grasses

The invasion by three different Utah populations of Pratylenchus neglectus (UTI, UT2, UT3) was similar in single and interplantings of ''Lahontan'' alfalfa and ''Fairway'' crested wheatgrass at 24 ñ 3 °C. Population UT3 was more pathogenic than UT1 and UT2 on both alfalfa and crested wheatgrass. Inoculum density was positively correlated with an invasion by P. neglectus. Invasions by UT3 at all initial populations (Pi) exceeded that of UT1 and UT2 for both single and interplanted treatments. The greatest reductions in shoot and root weights of alfalfa and crested wheatgrass were at a Pi of 8 P. neglectus/cm³ soil. Pi was negatively correlated with alfalfa and crested wheatgrass shoot and root growth and nematode reproduction. The reproductive factor (Rf) for UT3 exceeded that of UT1 and UT2 in single and interplantings at all inoculum levels. There were no differences in Rfin the Utah populations in single or interplantings. A nematode invasion increased with temperature and was greatest at 30 °C. Population UT3 was more pathogenic than UT1 and UT2 and reduced shoot and root growth at all soil temperatures. Populations UT1 and UT2 reduced shoot and root growth at 20-30 °C. Soil temperature was negatively correlated with shoot and root growth and positively correlated with nematode reproduction. Reproduction of UT3 exceeded that of UT1 and UT2 at all soil temperatures.     

Immunization with nonstructural proteins promotes functional recovery of alphavirus-infected neurons.

The encephalitic alphaviruses are useful models for understanding virus-neuron interactions. A neurovirulent strain of Sindbis virus (NSV) causes fatal paralysis in mice by infecting motor neurons and inducing apoptosis of these nonrenewable cells. Antibodies to the surface glycoproteins suppress virus replication, but other recovery-promoting components of the immune response have not been recognized. We assessed the effect on the outcome of NSV-induced encephalomyelitis of immunization of mice with nonstructural proteins (nsPs) by using recombinant vaccinia viruses. Mice immunized with vaccinia virus expressing nsPs and challenged with NSV initially developed paralysis similar to unimmunized mice but then recovered neurologic function. Mice preimmunized with vaccinia virus expressing structural proteins were completely protected from paralysis. Mice immunized with vaccinia virus alone showed paralysis with little evidence of recovery. Vaccinia virus expressing only nsP2 was as effective as vaccinia virus expressing all the nsPs. Protection provided by immunity to nsPs was not associated with a reduction in virus replication or with improved antibody responses to structural proteins. Protection could not be passively transferred with nsP immune serum. The depletion of T cells at the time of NSV infection decreased protection. The data show that antiviral immune responses can improve the ability of neurons to survive infection and to recover function without altering virus replication.     

High-frequency plant regeneration from seed-derived callus cultures of Kentucky bluegrass (Poa pratensis L.)

Shoot regeneration from seed-derived callus cultures of Kentucky bluegrass (Poa pratensis L.) was tested on MS basal medium supplemented with four different growth regulators. Regeneration frequencies for medium supplemented with 10 M 2,4-dichlorophenoxyacetic acid (2,4-D), 60 M 4amino-3, 5,6-picolinic acid (picloram), or 30 M 3,6dichloro-o-anisic acid (dicamba) ranged from 0.4 to 4%. Medium supplemented with 30 M dicamba plus 10 M 6-benzylaminopurine (BA) resulted in regeneration of shoots from 20% of the calli tested. Higher rates of growth regulators (60 or 90 M dicamba, 20 M BA) resulted in regeneration of shoots from 45% of calli of the cultivar Baron. In a subsequent study, the response of 12 North American cultivars grown on these media was cultivar-specific, with mean frequencies of regeneration ranging from 4% to 40%.Abbreviations 2,4-D 2,4-dichlorophenoxyaceticacid - dicamba 3,6-dichloro-o-anisic acid - picloram 4-amino-3,5,6-picolinic acid - BA 6-benzylaminopurine     

Affinity chromatography of the cellulase system of Trichoderma koningii.

A procedure involving affinity chromatography on cellulose was developed for separating enzymic components of the cellulase complex. Cellobiase, carboxymethylcellulase, component C2 and cellobiohydrolase are adsorbed with increasing tenacity, and released, as highly purified components, as the ionic strength of the eluent is decreased.     

Arginine deprivation in KB cells: I. Effect on cell cycle progress

When exponentially growing KB cells were deprived of arginine, cell multiplication ceased after 12 h but viability was maintained throughout the experimental period (42-48 h). Although tritiated thymidine ([(3)H]TdR) incorporation into acid-insoluble material declined to 5 percent of the initial rate, the fraction of cells engaged in DNA synthesis, determined by autoradiography, remained constant throughout the starvation period and approximately equal to the synthesizing fraction in exponentially growing controls (40 percent). Continous [(3)H]TdR-labeling indicated that 80 percent of the arginine-starved cells incorporated (3)H at some time during a 48-h deprivation period. Thus, some cells ceased DNA synthesis, whereas some initially nonsynthesizing cells initiated DNA synthesis during starvation. Flow microfluorometric profiles of distribution of cellular DNA contents at the end of the starvation period indicated that essentially no cells had a 4c or G2 complement. If arginine was restored after 30 h of starvation, cultures resumed active, largely asynchronous division after a 16-h lag. Autoradiographs of metaphase figures from cultures continuously labeled with [(3)H]TdR after restoration indicated that all cells in the culture underwent DNA synthesis before dividing. It was concluded that the majority of cells in arginine-starved cultures are arrested in neither a normal G1 nor G2. It is proposed that for an exponential culture, i.e. from most positions in the cell cycle, inhibition of cell growth after arginine with withdrawal centers on the ability of cells to complete replication of their DNA.     

Polyoma virus defective DNAs. I. Physical maps of a related set of defective molecules (D76, D91, D92).

Three related polyoma virus species, designated D92 (92% the size of full-length polyoma virus DNA), D91 (91%) and D76 (76%) have been analysed and their structures compared with that of polyoma virus A2 DNA. Three independent methods (restriction endonuclease cleavage, depurination fingerprinting and DNA-DNA hybridization) were used in the analysis.The defective DNAs appear to be: (1) entirely composed of viral sequences (no host DNA sequences were detected): (2) made up in part of long continuous sequences of DNA which appear identical to sequences of A2 DNA (D92 contains continuous sequences from 1 to 72 map units on the physical map of A2 DNA; that is, it contains the entire late region and part of the early region of the viral DNA. D91 and D76 contain those same sequences except for a 1% deletion around 18 map units): (3) made up in part of rearranged viral sequences.Several interesting features were noted about the rearranged sequences present in the defective DNAs. Sequences from the region around 67 map units were found linked to other (non-contiguous) regions of the DNA. Sequences from about 72 map units were linked to sequences from about 1 map unit. Multiple copies of sequences from 67 to 72 map units (from around the origin of DNA replication) were found (4 copies in D91 and D92, and 2 copies in D76).     

Radical mechanism of aminopyrine oxidation by cumene hydroperoxide catalyzed by purified liver microsomal cytochrome P-450

Under identical experimental conditions, purified preparations of rabbit liver microsomal cytochrome P-450 and beef heart metmyoglobin were equally effective at stimulating the oxidation of aminopyrine to a free radical species by cumene hydroperoxide. Mannitol had no effect on radical levels produced with either hemeprotein-hydroperoxide system; however, specific ligands of the two hemeproteins, substrates of cytochrome P-450, and phospholipid affected the two systems quite differently. Only the metmyo-globindependent oxidation of aminopyrine was significantly inhibited by fluoride and cyanide. Metyrapone, a specific ligand of cytochrome P-450, and benzphetamine, which was N-demethylated by cumene hydroperoxide only in the presence of cytochrome P-450, inhibited only the cytochrome P-450-stimulated oxidation of aminopyrine. Moreover, only with the solubilized liver hemeprotein was aminopyrine radical generation markedly stimulated by phospholipid. Similar properties of aminopyrine N-demethylation and radical formation by the cytochrome P-450-cumene hydroperoxide system have strongly implicated the radical as a requisite intermediate in product formation. Micromolar concentrations of metyrapone caused parallel inhibition, by at least 50%, of both radical generation and formaldehyde production. These results support a radical pathway of N-demethylation proposed for other hemeprotein-hydroperoxide systems (B. W. Griffin and P. L. Ting, 1978, Biochemistry, 17, 2206–2211), in which the substrate undergoes two successive one-electron abstractions, followed by hydrolysis of the iminium cation intermediate. Thus, for this class of substrates, the experimental data are consistent with the oxygen atom of the product arising from H₂O and not directly from the hydroperoxide, which has been previously proposed as a general mechanism for cytochrome P-450 peroxidatic activities.