Inhibition of ecdysis in Oncopeltus fasciatus by 2-acetylpyridine thiosemicarbazones

[1-(2-Pyridinyl)ethylidene]hydrazide of 1-pyrrolidinecarbothioic acid (AI3-63967) and seven similar thiosemicarbazones applied topically to Oncopeltus fasciatus were toxic or prevented ecdysis in fifth instars without the appearance of supernumerary nymphs. Treatments with AI3-63967 did not affect weight gain of the nymphs but delayed by 2 days the rise in hemolymph ecdysteroids and reduced their maximal titer by ca. 40%. Restoration of the ecdysteroid titer by injections of makisterone A or 20-hydroxyecdysone did not prevent the molting aberrations. Treated fourth instars exhibited incomplete ecdysis followed by death and treated adults died within 9 days post-treatment. Apparently, this group of thiosemicarbazones acts by a mechanism different from that of juvenile hormone mimics or chitin synthesis inhibitors.     

Thunderstorms: an important mechanism in the transport of air pollutants

Acid deposition and photochemical smog are urban air pollution problems, and they remain localized as long as the sulfur, nitrogen, and hydrocarbon pollutants are confined to the lower troposphere (below about 1-kilometer altitude) where they are short-lived. If, however, the contaminants are rapidly transported to the upper troposphere, then their atmospheric residence times grow and their range of influence expands dramatically. Although this vertical transport ameliorates some of the effects of acid rain by diluting atmospheric acids, it exacerbates global tropospheric ozone production by redistributing the necessary nitrogen catalysts. Results of recent computer simulations suggest that thunderstorms are one means of rapid vertical transport. To test this hypothesis, several research aircraft near a midwestern thunderstrom measured carbon monoxide, hydrocarbons, ozone, and reactive nitrogen compounds. Their concentrations were much greater in the outflow region of the storm, up to 11 kilometers in altitude, than in surrounding air. Trace gas measurements can thus be used to track the motion of air in and around a cloud. Thunderstorms may transform local air pollution problems into regional or global atmospheric chemistry problems.     

Elemental and redox analysis of single bacterial cells by x-ray microbeam analysis

High-energy x-ray fluorescence measurements were used to make elemental maps and qualitative chemical analyses of individual Pseudomonas fluorescens strain NCIMB 11764 cells. Marked differences between planktonic and adhered cells were seen in the morphology, elemental composition, and sensitivity to Cr(VI) of hydrated cells at spatial scales of 150 nm. This technology can be applied to natural geomicrobiological systems.     

A high-resolution radiation hybrid map of the human genome draft sequence

We have constructed a physical map of the human genome by using a panel of 90 whole-genome radiation hybrids (the TNG panel) in conjunction with 40,322 sequence-tagged sites (STSs) derived from random genomic sequences as well as expressed sequences. Of 36,678 STSs on the TNG radiation hybrid map, only 3604 (9.8%) were absent from the unassembled draft sequence of the human genome. Of 20,030 STSs ordered on the TNG map as well as the assembled human genome draft sequence and the Celera assembled human genome sequence, 36% of the STSs had a discrepant order between the working draft sequence and the Celera sequence. The TNG map order was identical to one of the two sequence orders in 60% of these discrepant cases.     

Specific tropism of HIV-1 for microglial cells in primary human brain cultures

Human immunodeficiency virus (HIV) frequently causes neurological dysfunction and is abundantly expressed in the central nervous system (CNS) of acquired immunodeficiency syndrome (AIDS) patients with HIV encephalitis or myelopathy. The virus is found mostly in cells of the monocyte-macrophage lineage within the CNS, but the possibility of infection of other glial cells has been raised. Therefore, the effects of different HIV-1 and HIV-2 strains were studied in primary cultures of adult human brain containing microglial cells, the resident CNS macrophages, and astrocytes. These cultures could be productively infected with macrophage-adapted HIV-1 isolates but not with T lymphocyte-adapted HIV-1 isolates or two HIV-2 isolates. As determined with a triple-label procedure, primary astrocytes did not express HIV gag antigens and remained normal throughout the 3-week course of infection. In contrast, virus replicated in neighboring microglial cells, often leading to their cell fusion and death. The death of microglial cells, which normally serve immune functions in the CNS, may be a key factor in the pathogenesis of AIDS encephalitis or myelopathy.     

Genetics and molecular mapping of the naked grains in hexaploid oat

Avena sativa L. subsp. nudisativa has the ability to produce naked grains. Genetic studies on the naked trait of oat began over a century ago, but the genetic and molecular factors associated with the expression of this trait have not been fully clarified. The objectives of this study were to evaluate the naked trait in two oat populations of recombinant inbred lines (RILs), to determine the number of genes, to estimate the heritability, and to map genomic regions associated with the naked trait in hexaploid oat. Parental lines and RILs of each population were screened for the naked trait from plants grown in the field over a 2 year period. Based on the phenotypic data, the oat RILs were classed as naked, partially naked, partially hulled and hulled. In both populations and years, a great number of RILs showed variable expressivity for the naked trait. The genetic analysis indicated the action of a major gene (N1) with the action of modifying genes controlling the formation of naked grains. The results of the estimate of heritability show that environmental conditions do not have a great influence in determining the naked trait. The quantitative trait loci analysis detected a genomic region with a large effect on the naked trait that explained more than 50% of the phenotypic variation. Further studies are needed to validate the use of these molecular markers to assist breeding programs to select high quality and stable naked oat cultivars.