Interaction of formamidines with octopamine-sensitive adenylate cyclase receptor in the nerve cord of Periplaneta americana L

Chlordimeform (CDM) and demethylchloridimeform (DCDM) mimic the action of octopamine in elevating adenylate cyclase activity in intact nerve cords of the American cockroach, Periplaneta americana. At a concentration of 1 x 10(-5)M, DCDM (13.5x increase within 20 minutes) is a more potent effector of the response than CDM (3x increase within 20 minutes), but both compounds show less efficacy than octopamine (23.5x increase within 15 minutes). DCDM also mimics the stimulatory effect of octopamine on adenylate cyclase activity in nerve cord homogenates whereas CDM has no demonstrable effect on this preparation. The octopamine- and DCDM-induced responses are competitively inhibited by phentolamine (1 x 10(-6)M) and cyproheptadine (1 x 10(-6)M) but not by propranolol (1 x 10(-6)M). DCDM and CDM inhibit the octopamine-induced activation of adenylate cyclase by 33% and 44% respectively. The results are discussed in light of the proposal that DCDM serves as a partial agonist and CDM as an antagonist of the octopamine receptor.     

Determination of the execution points of mutations in the nuclear replication cycle of Aspergillus nidulans.

Cultures of nuclear replication cycle mutants of Aspergillus nidulans were transferred to the nonpermissive temperature, and the fraction of nuclei still able to reach mitosis was determined. For the determinations, benomyl [methyl-1(butylcarbomoyl)benzimidazolecarbamate] was added to trap nuclei in mitosis, and these were detected by staining with aceto-orcein. The assumptions and controls required to relate the experimentally determined fractions to the points where a mutation blocks the nuclear cycle are discussed. Nine genetically distinct mutants were tested. Two of these were blocked early in the cycle, two in the middle, and five close to, or during, mitosis.     

Severe acute respiratory syndrome coronavirus evades antiviral signaling: role of nsp1 and rational design of an attenuated strain

The severe acute respiratory syndrome (SARS) epidemic was caused by the spread of a previously unrecognized infectious agent, the SARS-associated coronavirus (SARS-CoV). Here we show that SARS-CoV could inhibit both virus- and interferon (IFN)-dependent signaling, two key steps of the antiviral response. We mapped a strong inhibitory activity to SARS-CoV nonstructural protein 1 (nsp1) and show that expression of nsp1 significantly inhibited the activation of all three virus-dependent signaling pathways. We show that expression of nsp1 significantly inhibited IFN-dependent signaling by decreasing the phosphorylation levels of STAT1 while having little effect on those of STAT2, JAK1, and TYK2. We engineered an attenuated mutant of nsp1 in SARS-CoV through reverse genetics, and the resulting mutant virus was viable and replicated as efficiently as wild-type virus in cells with a defective IFN response. However, mutant virus replication was strongly attenuated in cells with an intact IFN response. Thus, nsp1 is likely a virulence factor that contributes to pathogenicity by favoring SARS-CoV replication.     

Speciation by postzygotic isolation: forces, genes and molecules

New species arise as reproductive isolation evolves between diverging populations. Here we review recent work in the genetics of postzygotic reproductive isolation-the sterility and inviability of species hybrids. Over the last few years, research has taken two new directions. First, we have begun to learn a good deal about the population genetic forces driving the evolution of postzygotic isolation. It has, for instance, become increasingly clear that conflict-driven processes, like sexual selection and meiotic drive, may contribute to the evolution of hybrid sterility. Second, we have begun to learn something about the identity and molecular characteristics of the actual genes causing hybrid problems. Although molecular genetic data are limited, early findings suggest that "speciation genes" correspond to loci having normal functions within species and that these loci sometimes diverge as a consequence of evolution in gene regulation.     

LIFE-HISTORY ADAPTATION AND REPRODUCTIVE ISOLATION IN A GRASSHOPPER HYBRID ZONE

Patterns of life-history adaptation and reproductive isolation were investigated in the acridid grasshoppers Melanoplus sanguinipes and M. devastator, which hybridize along an altitudinal gradient in the Sierra Nevada of California. Melanoplus sanguinipes females crossed with M. devastator males produced eggs that were approximately half as viable as eggs from other crosses. Diminished viability was not attributable either to infection by Wolbachia pipientis or to failure of sperm transfer. When offered an opportunity to choose a mate, females from all populations discriminated against males of the other species, whereas in no-choice tests measuring copulation duration only females from the tails of the clines showed preferences. Melanoplus sanguinipes, found at high elevations where the growing season is short, exhibited faster egg hatch, faster larval development, smaller adult body sizes, and smaller clutch sizes than M. devastator. Melanoplus devastator, from California's Central Valley, endured a hot and dry summer in a reproductive diapause that was absent in M. sanguinipes. Clines in reproductive diapause and clutch size coincided with the region of reproductive incompatibility. Development time, body size, and hatch time also changed across the hybrid zone, but the regions of largest transitions in these traits were either difficult to locate using the limited populations studied here or were not coincident with the zone's center. A method is described for combining ecological and phylogenetic analyses to address the unknown issue of whether life-history divergence has conributed to reproductive isolation in this system.     

Design and evaluation of a novel flow chamber for measuring cell adhesion to absorbable polymer films

There is great interest in improving cellular attachment to synthetic materials, particularly for developing small diameter tissue-engineered vascular grafts. However, limited research has been conducted to evaluate the adhesion characteristics of different cell types to absorbable substrates. Tissue engineered vessels typically fail as a result of delamination of the endothelial cell layer when exposed to fluid or blood flow. The focus of this research was to design and evaluate a flow chamber, using fibroblasts, smooth muscle cells, and endothelial cells, to probe the bounds of the system. A flow chamber was designed and fabricated to compare the relative adhesion characteristics of cells to absorbable polymer films. A preliminary investigation of mouse fibroblast (3T3M) adhesion to semicrystalline poly-L-lactide (PLL) films was conducted to determine general operating specifications. Cell coverage on films was evaluated using a live-dead assay and image analysis; following exposure to flow, tests were similarly conducted. Based on these results, additional studies were conducted to compare the adhesion of rat aortic smooth muscle cells (SMC) and endothelial cells (EC) on PLL films.     

Epitope spreading to citrullinated antigens in mouse models of autoimmune arthritis and demyelination

Introduction  

Anti-citrullinated protein antibodies have a diagnostic role in rheumatoid arthritis (RA); however, little is known about their origins and contribution to pathogenesis. Citrullination is the post-translational conversion of arginine to citrulline by peptidyl arginine deiminase, and increased citrullination of proteins is observed in the joint tissue in RA and in brain tissue in multiple sclerosis (MS).