Temperature,deltamethrin-resistance status and performance measures of Plutella xylostella: complex responses of insects to environmental variables

1. Worldwide, the excessive use of insecticides has resulted in field-evolved insecticide-resistant populations of diamondback moth (DBM), Plutella xylostella. A deltamethrin-resistant DBM population from the field was divided into two subpopulations in the laboratory. One population (S-strain) was maintained with no further exposure to insecticides, whereas the other population (R-strain) was maintained under a regime of intermittent selection with deltamethrin. 2. Individuals from both strains were reared at constant temperatures in the range 10–35 °C in the absence of deltamethrin, and the effects of rearing temperature on various traits were investigated. At the time of experimentation, the R-strain was 20-fold more resistant to deltamethrin than the S-strain. 3. Temperature differentially affected developmental time, adult life span, pupal weight, and fecundity of both strains. Although both strains laid eggs after being reared at 10 °C, few of these eggs were fertile. The R-strain developed significantly faster than the S-strain. The integrated performance of the S-strain and R-strain was greatest at 25 and 15 °C, respectively. 4. The present study provides important information on the complexities of the outcomes of the interactions between ectotherms and temperature. Specifically, temperature-trait relationships may not be unimodal, and ectotherm genotypes (in this case insecticide-resistance status) and abiotic stresses can interact with unpredictable outcomes. 5. Current models predicting DBM population dynamics and relative abundance in different locations do not consider different thermal biologies of different genotypes. The present study shows the dramatic effects of environment on many parameters used in these models and will help to enhance their accuracy, and thus their utility.     

Active human tissue plasminogen activator secreted from insect cells using a baculovirus vector

A baculovirus expression vector was constructed with the tissue plasminogen activator (TPA) cDNA under the control of the viral polyhedrin promoter. After infection of insect cells with the recombinant baculovirus, active TPA was secreted into the medium in which these cells were grown. TPA was isolated from the conditioned media using metal chelate affinity chromatography followed by immunoaffinity purification using mouse monoclonal anti-human TPA coupled to Sepharose. Sodium dodecyl sulfate-gel electrophoresis under reducing conditions and sequence analysis of recombinant human TPA have revealed a two-chain form of the enzyme. The N-terminal amino acid was identified to be serine, indicating that it was processed at its N-terminus by the insect cell culture in a manner similar to that observed for mammalian cells. The relative specific activity of recombinant TPA from insect cells is comparable to that of Bowes melanoma TPA standard. Its activity is stimulated in the presence of fibrinogen fragments, but by a factor about 2.3-fold lower than the Bowes melanoma TPA. The apparent molecular weight of recombinant TPA from insect cells was about 60K by fibrin agar activity gels, suggesting less complex glycosylation than recombinant TPA from mammalian cells.     

Highly selective chemical modification of cruciform loops by diethyl pyrocarbonate.

Diethyl pyrocarbonate reacts with the single-stranded loops of cruciform structures with great selectivity. Adenine bases are carbethoxylated, as a result of which the backbone may be cleaved with piperidine, and the level of chemical modification at each base may be determined. We have studied the ColE1 and (A-T)34 cruciforms of pColIR315 and pXG540. In each case we observe maximal modification at the most central adenosine of the loop, and an overall pattern of modification corresponding to a total loop size of about six bases. The results may be interpreted in terms of a model in which the loop has a defined tertiary structure. No modification was detected at either cruciform four-way junction, suggesting that this region is fully base-paired.     

Cytogenetic characterization of 20 lymphoblastoid lines derived from human individuals differing in bleomycin sensitivity

Summary Forty lymphoblastoid (lymphoid) lines were established from 42 volunteer blood donors, including healthy individuals and patients with head and neck carcinomas. Each peripheral blood sample was split into two portions, one for the establishment of a lymphoid line and the other for short-term culture, which was used to estimate bleomycin sensitivity by cytogenetic procedures. Twenty lymphoid lines were selected at random to compare bleomycin sensitivity with data obtained from short-term lymphocyte cultures. In each set, bleomycin sensitivity of lymphoid cells was similar to that of the lymphocytes. The lymphoid lines, which can be propagated for an unlimited supply of relatively homogeneous cellular material, will be useful for a variety of future investigations. This investigation was supported by grants from the John S. Dunn Foundation, Houston, TX, the Esther Knispel Fund administered by The University of Texas M. D. Anderson Cancer Center, Houston, TX, and Department of Health and Human Services PHS grant DE 07007.     

Overexpressions of cDNAs for β-Amyloid Precursor Proteins 695, 751, and 770 Enhance the Secretion of β-Amyloid Precursor Protein Derivatives and the Survival of P19-Derived Neurons

Abstract: P19 is a C3H mouse-derived line of multipotent embryonic carcinoma cells that differentiate into neural cells. P19 cell clones overexpressing the three major forms of β-amyloid precursor protein from their cDNA constructs were established. Unlike a previous study in which P19-derived neurons had a limited α-secretase activity, all of these clones produced significant amounts of secreted β-amyloid precursor protein. When treated with retinoic acid, these transformed lines differentiated into neurons and survived better than did nontransformed parental P19 cells. Furthermore, P19-derived neurons survived better in medium conditioned by the transformed P19 line, and survival was reduced by immunoabsorption with an antibody to β-amyloid precursor protein. These results suggest neurotrophic effects of secreted β-amyloid precursor protein and contrast with a previous report in which overexpression of a full-length cDNA for β-amyloid precursor protein led to degeneration of P19-derived neurons. Western blot analysis suggested that this difference might result from different levels of expression of putative neurotoxic C-terminal fragments of β-amyloid precursor protein; moreover, P19-derived neurons differ from P19 stem cells in the processing of these C-terminal fragments.     

Characterization of a Kinesin-Related Gene ATSV, within the Tuberous Sclerosis Locus (TSC1) Candidate Region on Chromosome 9Q34

In the search for candidate genes for the tuberous sclerosis (TSC1) disease locus on chromosome 9q34, we have isolated an overlapping series of 22 plasmid and phage cDNA clones covering nearly 7 kb and with an open reading frame of 5070 bp encoding a protein of 1690 amino acids. The putative protein product is a member of the kinesin superfamily and is homologous to the mouse KIF1A and theCaenorhabditas elegansunc-104 genes. Both KIF1A and unc-104 function in the anterograde axonal transport of synaptic vesicles. The human homolog is therefore termed H-ATSV (axonal transporter of synaptic vesicles, HGMW-approved nomenclature ATSV) Screening of DNA from 107 tuberous sclerosis patients and 80 unaffected individuals with H-ATSV cDNA probes by pulsed-field gel electrophoresis/Southern blotting following digestion by rare-cutting methylation-sensitive restriction enzymes showed variant banding patterns in three patients with tuberous sclerosis. However, further analysis indicated that these variant fragments represent a rare polymorphism probably associated with methylation of clustered restriction sites. There is no evidence to support H-ATSV as a candidate gene for TSC1.     

Mutational analysis of the capsid protein of Leishmania RNA virus LRV1-4.

The virion of Leishmania RNA virus is predicted to be composed of a 742-amino-acid major capsid protein and a small percentage of capsid-polymerase fusion molecules. Recently, the capsid protein alone was expressed and shown to spontaneously assemble into viruslike particles. Since the major structural protein of the virion shell self-assembles into viruslike particles when expressed in the baculovirus expression system, assembly of the virion can be studied by mutational analysis and expression of a single open reading frame. In this study, several deletions and one addition of the capsid protein of Leishmania RNA virus LRV1-4 were generated. These mutants show different degrees of assembly. Assembly domains are being identified such that the capsid protein may be used as a macromolecular packaging and delivery system for Leishmania species.