Thermoadaptive influence on reactivity pattern of vasopressinergic neurons in the guinea pig

Summary In cold-adapted guinea pigs, increased amounts of arginine-vasopressin (AVP) immunoreactive material could be visualized in neurons of the supraoptic and paraventricular nucleus, in fibers projecting to the neurohypophysis and in fiber terminals in the ventral lateral septum and in the amygdala. In warm-adapted animals the reactivity to AVP antiserum was poor in all neuronal structures examined. High AVP-immunoreactivity was accompanied by a reduced febrile response to bacterial pyrogen in cold-adapted guinea pigs.     

Rapid effects of insulin on cyclic GMP location in an intact protozoan

We studied rapid changes in location of cyclic GMP inTetrahymena pyriformis. Insulin caused cGMP localization in cilia and near the plasma membrane (0.5–1 min). Later (1–5 min) cGMP localization was diffuse in cytoplasm with perinuclear accentuation. Inactive insulin analogs did not elicit these changes.     

Control of gene expression by a natural metabolite-responsive ribozyme

Most biological catalysts are made of protein; however, eight classes of natural ribozymes have been discovered that catalyse fundamental biochemical reactions. The central functions of ribozymes in modern organisms support the hypothesis that life passed through an 'RNA world' before the emergence of proteins and DNA. We have identified a new class of ribozymes that cleaves the messenger RNA of the glmS gene in Gram-positive bacteria. The ribozyme is activated by glucosamine-6-phosphate (GlcN6P), which is the metabolic product of the GlmS enzyme. Additional data indicate that the ribozyme serves as a metabolite-responsive genetic switch that represses the glmS gene in response to rising GlcN6P concentrations. These findings demonstrate that ribozyme switches may have functioned as metabolite sensors in primitive organisms, and further suggest that modern cells retain some of these ancient genetic control systems.     

The afterglow and elliptical host galaxy of the short gamma-ray burst GRB 050724

Despite a rich phenomenology, gamma-ray bursts (GRBs) are divided into two classes based on their duration and spectral hardness--the long-soft and the short-hard bursts. The discovery of afterglow emission from long GRBs was a watershed event, pinpointing their origin to star-forming galaxies, and hence the death of massive stars, and indicating an energy release of about 10(51) erg. While theoretical arguments suggest that short GRBs are produced in the coalescence of binary compact objects (neutron stars or black holes), the progenitors, energetics and environments of these events remain elusive despite recent localizations. Here we report the discovery of the first radio afterglow from the short burst GRB 050724, which unambiguously associates it with an elliptical galaxy at a redshift z = 0.257. We show that the burst is powered by the same relativistic fireball mechanism as long GRBs, with the ejecta possibly collimated in jets, but that the total energy release is 10-1,000 times smaller. More importantly, the nature of the host galaxy demonstrates that short GRBs arise from an old (> 1 Gyr) stellar population, strengthening earlier suggestions and providing support for coalescing compact object binaries as the progenitors.     

Titan Radar Mapper observations from Cassini's T3 fly-by

Cassini's Titan Radar Mapper imaged the surface of Saturn's moon Titan on its February 2005 fly-by (denoted T3), collecting high-resolution synthetic-aperture radar and larger-scale radiometry and scatterometry data. These data provide the first definitive identification of impact craters on the surface of Titan, networks of fluvial channels and surficial dark streaks that may be longitudinal dunes. Here we describe this great diversity of landforms. We conclude that much of the surface thus far imaged by radar of the haze-shrouded Titan is very young, with persistent geologic activity.     

Cell-free synthesis and processing of multiple precursors to glucagon

Glucagon, a polypeptide hormone of 29 amino acids, is synthesized in the islets of Langerhans and immunoreactive forms of the molecule have been found in several tissues. Like many other polypeptide hormones, glucagon is synthesized via a larger precursor molecular, proglucagon; however, estimates of its size vary considerably and the biosynthetic relationship between some of the putative precursors and authentic secreted glucagon is unclear. Consequently it was of interest to investigate the primary translation product of glucagon mRNA to relate its size to that of previously described glucagon precursors. Here we provide evidence for three distinct immunoreactive preproglucagon molecules, two of which have an apparent molecular weight (MW) of approximately 16,000 (16K). Furthermore, when microsomal membranes were present during translation, the nascent 14K preproglucagon polypeptides were processed to proglucagon with a higher apparent MW of 15,000. In contrast, the nascent 16K preproglucagon was co-translationally processed to a slightly smaller polypeptide. The data indicate that the 14K and 16K preproglucagons undergo different types of post-translational modification.     

The genome of the model beetle and pest Tribolium castaneum

Tribolium castaneum is a member of the most species-rich eukaryotic order, a powerful model organism for the study of generalized insect development, and an important pest of stored agricultural products. We describe its genome sequence here. This omnivorous beetle has evolved the ability to interact with a diverse chemical environment, as shown by large expansions in odorant and gustatory receptors, as well as P450 and other detoxification enzymes. Development in Tribolium is more representative of other insects than is Drosophila, a fact reflected in gene content and function. For example, Tribolium has retained more ancestral genes involved in cell-cell communication than Drosophila, some being expressed in the growth zone crucial for axial elongation in short-germ development. Systemic RNA interference in T. castaneum functions differently from that in Caenorhabditis elegans, but nevertheless offers similar power for the elucidation of gene function and identification of targets for selective insect control.     

Stable expression of two variable surface glycoproteins by cloned Trypanosoma equiperdum

African trypanosomes are thought to evade the host immune system by periodically changing their variable surface glycoprotein (VSG). VSG genes are activated by a complex process involving the duplicative transposition of silent basic copy genes to one of several expression sites. These expression-linked copies (ELCs) of the VSG genes are also subject to regulation within expression sites by as yet unknown mechanisms. It is generally assumed that trypanosomes can express only one VSG gene at a time. Nevertheless, the finding that they contain multiple VSG gene expression sites suggests that multiple expression is possible. We show here that Trypanosoma equiperdum can stably express two VSG genes in a simple axenic culture system and that both antigens are present on the cell surface. The two antigens do not co-cap or form heterodimers. Their corresponding genes show no cross-hybridization and are situated in different telomere-linked expression sites. Northern blot analysis reveals that both genes are active in the double expressors.