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PubMedDate not supplied

Immunoaffinity purification of the neuropeptide prothoracicotropic hormone from Manduca sexta.

The prothoracicotropic hormones (PTTH) are cerebral peptides that control insect postembryonic development by stimulating the prothoracic glands to synthesize ecdysteroids. Using immunoaffinity chromatography and SDS-PAGE, a 25.5 kDa big PTTH has been purified from Manduca sexta. Based upon SDS-PAGE and Western blot analysis, the native form of big PTTH appears to be a dimer with monomers of 16.5 kDa. Four HPLC-separated fragments of this acidic peptide were sequenced and exhibited no sequence similarity with Bombyx mori PTTH. In agreement with this finding, the basic Bombyx PTTH had no PTTH bioactivity in Manduca. One sequenced fragment of the Manduca PTTH is approximately 70% similar to the vertebrate cellular retinoid binding proteins, suggesting these binding proteins may be present in insects.

Amino Acid Sequence↗
PubMed1989

Maserlike nonlinear scatter from human breath, a surface-enhanced far infrared scatter effect.

A cotton tip applicator was utilized to stimulate far IR scatter (emission) from human breath. The reticulated cotton tip was vibrated at 200 Hz, the acoustic frequency that matches the average vibration frequency of common species of mosquitoes. Mosquitoes have open resonator dielectric sensillae (spines) on their antenna that match the 643 cm-1 (15.5) Cabannes line in the 667 cm-1 region of CO2 rotation line, acoustic Stokes Brillouin and Stokes Raman lines are noted. Implications of such maserlike (coherent or partial coherent) scatter lines to insect control and disease diagnostics are discussed.

Animals↗
PubMed1995

Pyrethroids, nerve poisons: how their risks to human health should be assessed.

The extensive worldwide efforts of structural modification of natural pyrethrins for better performances have resulted in successful development of a wide variety of synthetic pyrethroids with tremendously high efficacy, knock-down activity or vapor action, and/or with acceptable environmental stability and safety. Currently these pyrethroids including their preferentially manufactured stereoisomers are widely used in agriculture, and for public health as well as household insect control. The detailed toxicology and metabolism studies intended to attain human risk assessment have revealed that with voltage-dependent sodium channel as target site pyrethroids induce pronounced repetitive activity characterized grossly by tremor, hypersensitivity, choleoathetosis, and salivation. In addition, so-called cyano-pyrethroids cause transient skin paresthesia in workers. With regard to tumorigenicity, mutagenicity, teratogenicity and developmental toxicity, no significant findings have been reported. Pyrethroids are eliminated from the animals quite rapidly and completely, undergoing oxidation and ester hydrolysis followed by various conjugations, with low tissue residues. Thus, overall, sound scientific bases exist for human risk assessment under the present usage conditions.

Animals↗
PubMed1990

A survey of medicinal plants of minas gerais. Brazil.

A list of fifty-two plant species used for medicinal purposes or to control arthropods by peasants near Belo Horizonte, Minas Gerais (Brazil) has been compiled. Preparation procedures are also noted. The use of plants for controlling insects and to heal a condition known as "ferida brava" is discussed. The role of indigenous plant remedies within the local health care system is worthy of a closer investigation.

Botany↗
PubMed1994

Linkage of kdr-type resistance and the para-homologous sodium channel gene in German cockroaches (Blattella germanica).

Pyrethroids are an important class of insecticides for controlling insect pests, including the German cockroach. Unfortunately, many insects have developed resistance to pyrethroids. One of the most important mechanisms of resistance is kdr (knockdown resistance) which is characterized by neural insensitivity to pyrethroids and DDT. To investigate whether the voltage-dependent sodium channel is involved in kdr-type resistance in the German cockroach, we isolated a 120 bp DNA fragment of the para-homologous sodium channel gene from German cockroaches. Using this fragment as a probe, we identified a restriction fragment length polymorphism (RFLP) of the para-homologous sodium channel gene between susceptible and kdr-type resistant German cockroaches. RFLP analysis of F2 and backcross cockroach populations (total of 331 individuals) showed that all homozygous resistant individuals had a 3.7 kb EcoRI fragment, all homozygous susceptible individuals had a 3.0 kb EcoRI fragment, and all heterozygous individuals had both 3.7 and 3.0 kb fragments. No recombination was detected between the kdr-type resistance locus and the para-homologous sodium channel gene. This suggests that the kdr-type resistance locus and para-homologous sodium channel gene are identical or tightly linked (< 0.2 cM) in German cockroaches. Our results provide strong evidence that modification of para-homologous sodium channels is associated with kdr-type resistance.

Amino Acid Sequence↗
PubMed1995

Stereospecific, mechanism-based, suicide inhibition of a cytochrome P450 involved in ecdysteroid biosynthesis in the prothoracic glands of Manduca sexta.

The first required step in ecdysteroid (molting hormone) biosynthesis, dietary cholesterol (C) conversion to 7-dehydrocholesterol (7dC) via 7,8-dehydrogenation, is mediated by a microsomal cytochrome-P450 monooxygenase specific to the larval prothoracic gland. A subsequent series of unknown "black-box" oxidations of 7dC result in the unusual ring geometry (cis-A/B) and functionality (6-keto-7-ene-14-alpha-ol) of the ecdysteroids and has been thought to involve the initial formation of alpha-5,6-epoxy-7-dehydrocholesterol (alpha epo7dC). Pharmacological studies indicated that conversion of C to 7dC in prothoracic gland homogenates was strongly and equally inhibited by the isomeric cholesterol substrate analogues alpha- and beta-5,6-epoxycholesterol (alpha- and beta epoC) and alpha- and beta-5,6-iminocholesterol (alpha- and beta iminoC). With respect to the conversion of C to ecdysteroids by disrupted glands, however, the two alpha-isomeric substrates were 10-fold more inhibitory than were their beta-analogues. Indeed, alpha amino C was as active as the non-specific pyrimidyl cytochrome-P450 monooxygenase inhibitor fenarimol that shows moderate toxicity in many insect species. All four cholesterol analogues competitively inhibited cholesterol 7,8-dehydrogenation, but only alpha epoC and possibly alpha iminoC were desaturated to delta 7-products. Although the KmS (and KiS) for all the substrates were similar (1.7-6.0 x 10(-5) M), the Vmax for alpha epoC dehydrogenation was eight-fold higher than that of C, making it a superior substrate for following this reaction in ecdysteroidogenic tissues rich in endogenous C. The 7,8-dehydrogenation of alpha epoC and alpha iminoC by prothoracic glands would produce the potentially reactive intermediates, alpha epo7dC and alpha imino7dC, respectively. They, in turn, could then undergo facile, acid-catalyzed ring-opening to the allylic-stabilized carbo-cation electrophiles. These very reactive, transient species, if formed in the active site of the monooxygenase, would then alkylate either the heme group or the apoprotein of the cytochrome or both, leading to the irreversible inhibition of the enzyme. The present data show that alpha epoC and probably alpha iminoC are mechanism-based suicide inhibitors of the enzyme catalyzing cholesterol 7,8-dehydrogenation and may be the prototypes of a new class of selective insect control agents.

Animals↗
PubMed1999

Monitoring house reinfestation by vectors of Chagas disease: a comparative trial of detection methods during a four-year follow-up.

Domestic reinfestations by triatomine bugs were monitored after application of deltamethrin and apparent elimination of Triatoma infestans in Amama and other nearby rural villages, north-west Argentina, from 1992 to 1996. The five methods used were sensor boxes, sheets of pink typing-paper, timed manual catches by a skilled three-person team aided by a flushing-out agent, collections by house-dwellers, and knockdown using insecticide fumigant canisters. In bedrooms, house-dwellers collected T. infestans significantly more frequently than the flushing-out method, but the reverse occurred in peridomestic sites. Both methods and sensor boxes revealed the frequent invasion of adult Triatoma guasayana and T. infestans, but neither T. guasayana nor Triatoma sordida colonized bedroom areas in spite of their rising abundance in nearby peridomestic sites. Sensor boxes were significantly more sensitive than the matched paper-sheets in three of five cross-sectional surveys. On average, each box recorded 2.0-3.2 times more triatomine fecal smears than each paper sheet. The frequency of dejecta in sensor boxes correlated positively with the proportion of houses where T. infestans, T. guasayana or T. sordida were captured by any method in bedroom areas. Triatomine fecal smears in sensor boxes were the earliest and most frequent sign of domiciliary infestation, followed by dwellers' collections of adult bugs. Analyzing the data prospectively, we provide a quantitative, predictive understanding of detection methods and review the validity and interpretation of the different signs of infestation obtained. The most sensitive and cost-effective combination of detection methods for vector surveillance in domestic areas was the use of sensor boxes and house-dwellers collections.

Animals↗
PubMed2001

The role of a proline-induced broken-helix motif in alpha-helix 2 of Bacillus thuringiensis delta-endotoxins.

Bacillus thuringiensis delta-endotoxins (Cry proteins), are widely used for insect control and plant protection. They are water-soluble proteins that insert into membranes forming ion channels. In most Cry toxins alpha-helix 2 is broken by a highly conserved proline residue (Pro70 in Cry1Ab), generating a broken-helix motif. The flexibility of the motif was altered through site-directed mutagenesis. It was found that increasing the flexibility of the motif decreased the stability, the ion transport ability and the toxicity of the protein. By removing the broken-helix motif, the biological properties were restored to a wild type level.

Alanine↗
PubMed1996

Infraspecific taxonomy and essential oil chemotypes in sweet basil, Ocimum basilicum.

Essential oil compositions of fresh and freeze-dried leaves were determined for 16 accessions of Ocimum basilicum belonging to different varieties to see whether they could be used as infraspecific taxonomic characters. One accession of O. x citriodorum was also studied. Some 30 monoterpenoids, sesquiterpenoids and phenylpropanoids were identified, the major components (more than 20% of the total essential oil composition in one or more accessions) being geranial and neral in O. x citriodorum, and linalool, methyl chavicol, eugenol, methyl eugenol and geraniol in O. basilicum. Based on a combination of the latter compounds, five major essential oil profiles could be distinguished in the accessions studied for O. basilicum. These profiles were largely the same for fresh and freeze-dried material of the same plant, although in the dried leaves, methyl chavicol and eugenol concentrations had generally declined in comparison to those of linalool. There appeared to be little correlation between essential oil patterns and varietal classification within O. basilicum. In view of the chemical heterogeneity of O. basilicum and its use as an essential oil-producing crop, culinary herb, medicinal plant and insect-controlling agent, in all of which chemicals play an important role, the infraspecific classification of this taxon should take chemical characters into consideration. A system for the classification of essential oil chemotypes in O. basilicum is proposed.

Gas Chromatography-Mass Spectrometry↗
PubMed2001

Chemical industry reduces emissions--from production to the consumer.

Responsible care has always been an important issue at a chemical industry like Bayer. In recent years, the company has made extensive efforts to further improve its products and processes with regard to environmental protection and safety. In this contribution, a number of examples will highlight recent achievements of Bayer in the field of low or no emission processes and products. Examples are given in the fields of production-integrated environmental protection measures (new and improved processes e.g., for the production of adipic acid), the application of integrated environmental protection measures (2K-PUR water-borne coatings for cars) and product-integrated environmental protection measures (targeted application of insecticides/Attract and Kill) as a new low emission method to control insect pests.

Air Pollution↗
PubMed2000

Extreme resistance to Potato leafroll virus in potato cv. Russet Burbank mediated by the viral replicase gene.

High levels of field resistance to Potato leafroll virus (PLRV; Genus: Polerovirus; Family: Luteoviridae) were achieved by expression of the unmodified, full-length PLRV replicase gene in potato plants cv. Russet Burbank. A high degree of resistance was also achieved, but less frequently, by expression of a truncated construct of the replicase gene. In limited testing, neither miss-frame nor antisense constructs of the replicase gene conferred resistance. The degree of resistance expressed among different transformant lines ranged from near immunity to full susceptibility. Resistance to the Colorado potato beetle (Leptinotarsa decemlineata Say) was combined with resistance to PLRV by expression of the cry3A insect control protein gene from Bacillus thuringiensis var. tenebrionis in combination with the unmodified, full-length, viral replicase gene. Resistance was expressed as a reduced incidence of infection detectable by foliage symptoms or serological tests. Reduced incidence of infection was not associated with a decrease in virus antigen concentration in the few plants of resistant lines that became infected. Virus was not detected in the foliage of symptomless plants but was detected in progeny plants produced from the tubers of inoculated but symptomless test plants of some resistant lines. The resistance was effective under natural exposure and against plant-to-plant spread of PLRV by the aphid vector, Myzus persicae Sulzer. Three of the resistant lines selected in these studies were released and are now in commercial production.

Antiviral Agents↗