Thromboxane A2 induces airway constriction through an M3 muscarinic acetylcholine receptor-dependent mechanism

Thromboxane A2 (TXA2) is a potent lipid mediator released by platelets and inflammatory cells and is capable of inducing vasoconstriction and bronchoconstriction. In the airways, it has been postulated that TXA2 causes airway constriction by direct activation of thromboxane prostanoid (TP) receptors on airway smooth muscle cells. Here we demonstrate that although TXA2 can mediate a dramatic increase in airway smooth muscle constriction and lung resistance, this response is largely dependent on vagal innervation of the airways and is highly sensitive to muscarinic acetylcholine receptor (mAChR) antagonists. Further analyses employing pharmacological and genetic strategies demonstrate that TP-dependent changes in lung resistance and airway smooth muscle tension require expression of the M2 mAChR subtype. These results raise the possibility that some of the beneficial actions of anticholinergic agents used in the treatment of asthma and chronic obstructive pulmonary disease result from limiting physiological changes mediated through the TP receptor. Furthermore, these findings demonstrate a unique pathway for TP regulation of homeostatic mechanisms in the airway and suggest a paradigm for the role of TXA2 in other organ systems.     

Expression and function of NPSR1/GPRA in the lung before and after induction of asthma-like disease

A genetic contribution to asthma susceptibility is well recognized, and linkage studies have identified a large number of genes associated with asthma pathogenesis. Recently, a locus encoding a seven-transmembrane protein was shown to be associated with asthma in founder populations. The expression of the protein GPRA (G protein-coupled receptor for asthma susceptibility) in human airway epithelia and smooth muscle, and its increased expression in a mouse model of asthma, suggested that a gain-of-function mutation in this gene increased the disease risk. However, we report here that the development of allergic lung disease in GPRA-deficient mice is unaltered. A possible explanation for this finding became apparent upon reexamination of the expression of this gene. In contrast to initial studies, our analyses failed to detect expression of GPRA in human lung tissue or in mice with allergic lung disease. We identify a single parameter that distinguishes GPRA-deficient and wild-type mice. Whereas the change in airway resistance in response to methacholine was identical in control and GPRA-deficient mice, the mutant animals showed an attenuated response to thromboxane, a cholinergic receptor-dependent bronchoconstricting agent. Together, our studies fail to support a direct contribution of GPRA to asthma pathogenesis. However, our data suggest that GPRA may contribute to the asthmatic phenotype by altering the activity of other pathways, such as neurally mediated mechanisms, that contribute to disease. This interpretation is supported by high levels of GPRA expression in the brain and its recent identification as the neuropeptide S receptor.     

Deaths of detainees in the custody of US forces in Iraq and Afghanistan from 2002 to 2005

In light of the large number of detainees who continue to be taken and held in US custody in settings with limited judicial or public oversight, deaths of detainees warrant scrutiny. We have undertaken the task of reviewing all known detainee deaths between 2002 and early 2005 based on reports available in the public domain. Using documents obtained from the Department of Defense through a Freedom of Information Act request, combined with a review of anecdotal published press accounts, 112 cases of death of detainees in United States custody (105 in Iraq, 7 in Afghanistan) during the period from 2002 to early 2005 were identified. Homicide accounted for the largest number of deaths (43) followed by enemy mortar attacks against the detention facility (36). Deaths attributed to natural causes numbered 20. Nine were listed as unknown cause of death, and 4 were reported as accidental or natural. A clustering of 8 deaths ascribed to natural causes in Iraq in August 2003 raises questions about the adequacy and availability of medical care, as well as other conditions of confinement that may have had an impact on the mortality rate.     

Can folic acid protect against congenital heart defects in down syndrome?

BACKGROUND: Several studies have suggested a protective effect of folic acid (FA) on congenital heart anomalies. Down syndrome (DS) infants are known to have a high frequency of heart anomalies. Not all children with DS suffer from heart anomalies, which raises the question whether maternal factors might affect the risk of these anomalies. Our objectives were to investigate whether first-trimester FA use protects against heart anomalies among DS children. METHODS: Women with liveborn DS children participating in the Slone Epidemiology Center Birth Defects Study between 1976 and 1997 were included. We performed case-control analyses using DS, with heart anomalies as cases and DS, without heart anomalies as controls. Subanalyses were performed for defects that have been associated with FA in non-DS populations (conotruncal, ventricular septal [VSD]) and for those that are associated with DS (ostium secundum type atrial septal defects [ASD] and endocardial cushion defects [ECD]). Exposure was defined as the use of any FA-containing product for an average of at least 4 days per week during the first 12 weeks of pregnancy, whereas no exposure was defined as no use of FA in these 12 weeks. RESULTS: Of the 223 cases, 110 (49%) were exposed versus 84 (46%) of the 184 controls. After adjustment for possible confounders, no protective effect of FA was found on heart anomalies overall (OR 0.95, 95% CI: 0.61-1.47) nor separately for conotruncal defects, VSDs, ASDs, or ECDs. CONCLUSIONS: Our study does not show a protective effect of FA on heart anomalies among infants with DS.     

Anti-RANKL therapy for inflammatory bone disorders: Mechanisms and potential clinical applications

Focal bone loss around inflamed joints in patients with autoimmune disease, such as rheumatoid arthritis, remains a serious clinical problem. The recent elucidation of the RANK/RANK-ligand/OPG pathway and its role as the final effector of osteoclastogenesis and bone resorption has brought a tremendous understanding of the pathophysiology of inflammatory bone loss, and has heightened expectation of a novel intervention. Here, we review the etiology of inflammatory bone loss, the RANK/RANK-ligand/OPG pathway, and the clinical development of anti-RANK-ligand therapy.     

Single linkage group per chromosome genetic linkage map for the horse, based on two three-generation, full-sibling, crossbred horse reference families

A genetic linkage map of the horse consisting of 742 markers, which comprises a single linkage group for each of the autosomes and the X chromosome, is presented. The map has been generated from two three-generation full-sibling reference families, sired by the same stallion, in which there are 61 individuals in the F2 generation. Each linkage group has been assigned to a chromosome and oriented with reference to markers mapped by fluorescence in situ hybridization. The average interval between markers is 3.7 cM and the linkage groups collectively span 2772 cM. The 742 markers comprise 734 microsatellite and 8 gene-based markers. The utility of the microsatellite markers for comparative mapping has been significantly enhanced by comparing their flanking sequences with the human genome sequence; this enabled conserved segments between human and horse to be identified. The new map provides a valuable resource for genetically mapping traits of interest in the horse.     

Loss of mitochondrial membrane potential is associated with increase in mitochondrial volume: physiological role in neurones

Mitochondrial volume homeostasis is a housekeeping cellular function, thought to help regulate oxidative capacity, apoptosis, and mechanical signaling. The volume is mainly regulated by potassium flux into and out of the matrix and controlled by the electrochemical potential. Mitochondrial depolarization will therefore affect this flux but studies showing how have not been consistent, and it is unclear what mitochondrial volume changes also occur. The aim of the present study was to investigate mitochondrial volume changes in permeabilized neurons under various bioenergetic conditions using deconvolution confocal microscopy. Under control conditions, mitochondria in situ appeared rod-shaped with mean length, surface area, and volume values of 2.29+/-0.10 microm, 1.41+/-0.10 microm2, and 0.062+/-0.006 microm3, respectively (n=42). Valinomycin, a K+-selective ionophore, increased mitochondrial volume by 63+/-22%, although surface area was almost unchanged because mitochondrial shape became more spherical. Pinacidil, an opener of mitochondrial ATP-dependent channels, produced similar effects, although some mitochondria were insensitive to its action. Mitochondrial depolarization with the protonophore FCCP, or with respiratory chain inhibitors antimycin and sodium azide was associated with a considerable increase in mitochondrial volume (by 75%-140%). Effects of mitochondrial modulators were also studied in intact neurones. Tracking of single mitochondria showed that during 65+/-2% of their time, mitochondria were motile with an average velocity of 0.19+/-0.01 microm/s. Antimycin, azide, and FCCP induced mitochondrial swelling and significantly decreased mitochondrial motility. In the presence of pinacidil, swollen mitochondria had reduced their motility, although mitochondria with normal volume stayed motile. These data show that mitochondrial depolarization was followed by significant swelling, which, in turn, impaired mitochondrial trafficking.     

Viscoelastic characterization of the porcine temporomandibular joint disc under unconfined compression

Pathophysiology of the temporomandibular joint (TMJ) disc is central to many orofacial disorders; however, mechanical characterization of this tissue is incomplete. In this study, we identified surface-regional mechanical variations in the porcine TMJ disc under unconfined compression. The intermediate zone, posterior, anterior, lateral, and medial regions of eight TMJ discs were sectioned into inferior and superior surface samples. Surface-regional sections were then subjected to incremental stress relaxation tests. Single strain step (SSS) and final deformation (FD) viscoelastic models were fit to experimental data. Both models represented the experimental data with a high degree of accuracy (R(2)=0.93). The instantaneous modulus and relaxation modulus for the TMJ disc sections were approximately 500 kPa and 80 kPa, respectively; the coefficient of viscosity was approximately 3.5 MPa-s. Strain dependent material properties were observed across the disc's surface-regions. Regional variations in stiffness were observed in both models. The relaxation modulus was largest in the inferior-medial parts of the disc. The instantaneous modulus was largest in the posterior and anterior regions of the disc. Surface-to-surface variations were observed in the relaxation modulus for only the FD model; the inferior surface was found to be more resistant to compression than the superior surface. The results of this study imply the stiffness of the TMJ disc may change as strain is applied. Furthermore, the lateral region exhibited a lower viscosity and stiffness compared to other disc regions. Both findings may have important implications on the TMJ disc's role in jaw motion and function.     

Genetic analysis of the structure and function of transfer messenger RNA pseudoknot 1

tmRNA rescues stalled ribosomes in eubacteria by forcing the ribosome to abandon its mRNA template and resume translation with tmRNA itself as a template. Pseudoknot 1 (pk1), immediately upstream of this coding region in tmRNA, is a structural element that is considered essential for tmRNA function based on the analysis of pk1 mutants in vitro. pk1 binds near the ribosomal decoding site and may make base-specific contacts with tmRNA ligands. To study pk1 structure and function in vivo, we have developed a genetic selection that ties the life of Escherichia coli cells to tmRNA activity. Mutation of pk1 at 20% per base and selection for tmRNA activity yielded sequences that retain the same pseudoknot fold. In contrast, selection of active mutants from 10(6) completely random sequences identified hairpin structures that functionally replace pk1. Rational design of a hairpin with increased stability using an unrelated sequence yielded a tmRNA mutant with nearly wild-type activity. We conclude that the role of pk1 in tmRNA function is purely structural and that it can be replaced with a variety of hairpin structures. Our results demonstrate that in the study of functional RNAs, the inactivity of a mutant designed to destroy a given structure should not be interpreted as proof that the structure is necessary for RNA function. Such mutations may only destabilize a global fold that could be formed equally well by an entirely different, stable structure.